We are currently at the peak of the Broad-winged Hawk fall migration, an annual event that birders look forward to with great anticipation. These birds are gregarious, often migrating in flocks or groups called “kettles” that range from several individuals to many thousands of birds. In New England in mid-September it’s possible to see 10,000 Broad-winged Hawks a day at a hawk watch site; near the Great Lakes, 50,000 a day and Texas hawk-watchers have been known to see 300,000 to 500,000 a day.
Broad-wings depend more on thermals, rising columns of warm air, during their migration than most raptors. They don’t usually begin flying until mid-morning, by which time the sun has created thermals, and they stop flying as soon as thermal production ceases in later afternoon. During the day kettles can be seen circling around and around, higher and higher as they ride thermal columns of air upwards, peeling off at the apex and soaring (saving energy other migrating hawks use flapping their wings) southwards towards their wintering grounds.
To find hawk watch sites in your part of the world, go to the Hawk Migration Association (http://www.hmana.org/hawk-watch-sites/).
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Broad-winged Hawk nestlings typically leave their nest sometime in July or early August, at about five to six weeks of age. The fledglings tend to stay within their parents’ territory for up to eight weeks. Much of the first two weeks after fledging is spent perched close to the nest, often returning to the nest for food delivered by the parents, but by the time the fledglings are about seven weeks old, they are capturing their own prey. This leaves the adults free to hunt for themselves, as they fly overhead emitting their high-pitched, shrill whistle. (Photos: adult Broad-winged Hawk)
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.